In summary, this article has presented evidence based on the known structure-activity relationships of psychoactive compounds and studies of several biochemical parameters as well as behavioral data in rats that show that MDMA and particularly MBDB do not fit into the pharmacological classification of hallucinogen or psychedelic. Furthermore, these compounds differ sufficiently in their biochemical pharmacology profiles to distinguish them from amphetamine. Therefore, if MDMA and MBDB are not hallucinogens and are not simply stimulants, what are they? Based on their unique human psychopharmacology, it is believed that they represent a new drug category. There is no other known class of psychoactive agents that produces effects similar to these compounds. Thus, the present author's research team has proposed that this new pharmacological class be designated entactogens.